Oh for <insert deity that you wish to disparage here>'s sake.

My training bike is an aluminium frame + carbon fork beasty and my previous training bike was a 1980's steelo, complete with fatigue. IMHO there is no (repeat NO) fargin difference between the two materials (yes, at the same bloody tyre pressure!) in terms of ride comfort if the build quality is satisfactory.

I'm sick of seeing wallys (who should know better) passing up one frame material against another without any credence and/or base knowledge. Subversive marketing doesn't belong on the forums. So here's how it is:

Steel is good
Titamium is good
Aluminium is good
Carbon Fibre is good

Spend what you like. Buy what you like. Just don't buy what you don't like: your arse will tell you.